This invention relates to the field of optical metrology, and includes an apparatus and method for rapidly and accurately measuring contours of test objects.
Prior art techniques of precisely determining the surface contours of objects have required formation of a conventional image of the object. The image is typically acquired by a video camera, digitized, and stored in a computer memory as a set of pixels. The computer then analyzes the image, such as by comparing it, pixel by pixel, with a stored reference image.
The processing of a stored image requires a very large number of calculations. Even with high-speed digital computers, processing a stored image takes a relatively long time, thereby limiting the ability of the system to generate immediate, "real time" results.
The systems of the prior art also have the disadvantage that they occupy relatively large amounts of space. The latter consideration is partly due to the size of the laser and associated optical equipment required. Also, many prior art systems for analyzing an object require that the object be moved relative to the source of laser light. Providing a moving platform for the object inherently increases the overall size of the system.
The present invention solves the problems described above, by providing a high-speed method and apparatus for analyzing the contour of a test object. The present invention does not use conventional image processing techniques; in fact, no image of the object is ever obtained or stored. The components used in the apparatus can be configured within a small optical head which can scan areas normally inaccessible to larger, conventional testing devices.